High voltage generating apparatus

ABSTRACT

A rod shaped varistor having a high breakdown voltage is connected across a source of high voltage so as to maintain the output voltage at a substantially constant value. The varistor is provided with a ring-shaped terminal for deriving an intermediate voltage which is adjustable by moving the ring-shaped terminal along the varistor.

O United States Patent 91 [m 3,716,778 Sato [451 Feb. 13, 1973 [54] HIGH VOLTAGE GENERATING 2,935,712 5/1960 Oppenheim et al. ..338/20 APPARATUS 2-2242: 17:22; 75] Inventor: Hideo Salo, Tokyo, Japan 557,209 6/1951 Valeton et a1. ....321/2 HF 3,377,426 4/1968 Thomas ..338/20 X [73] Asslgneez e2kl JOnkyo complny, 3,389,216 6/1968 Sennik ..338/20 X 0 yo, apan [22] Filed: April 7, 1971 Primary Examiner-Gerald (loldberg A l N 3 "95 Attorney-Chltti0k, Pfund, Birch, Samuels & Gauthier [30] Foreign Application Priority Data [57] ABSTRACT April 9, Japan A rod Shaped varistor having a breakdown l age is connected across a source of high voltage so as [52] US. Cl. ..323/8, 310/8, 315/27, to maintain the output voltage at a Substantially com 321/2 323/94 338/20 stant value. The varistor is provided with a ring- Clh p e mi for de i i g an i edia o tage [58] Fleld of Search .A 338/13, 20, 21, 31; 323/82 which is adjustable y moving the g p ten 323/22 94 i s/ 2 7 minal along the varistor.

[56] References Cited 7 UNITED STATES PATENTS 5 Claims, 8 Drawing Figures 2,796,505 6/1957 Bocciarclli ..338/20 F 3/ :r l g5 3 6 gm PATENTEDFEBI 3l975 sflEET 10F VARISTOR CURRENT Vs VOLTAGE V FIGZ FE VARISTOR INVENTOR HIDEO SATO ATTORNEYS PATENTEUFEBI 3197a SHEET 2 or a INVENTOR Y HIDEO S'ATO cQJC/g/ ya, BY W ZM -i ATTORNEYS PAIENTEBFEBI 3191a VARISTOR INVENTOR HIDEPO SATO ATTORNEY S HIGH VOLTAGE GENERATING APPARATUS BACKGROUND OF THE INVENTION This invention relates to high voltage generating apparatus which can be used as a high voltage generating circuit for a television receiving set, for example.

There have been proposed many types of high voltage generating apparatus including those utilizing a transformer or a piezoelectric transducer. However,

the voltage regulation of these prior art high voltage generating apparatus is generally poor, in other words, the output voltage varies greatly with variation in the load connected thereto. Accordingly, it is necessary to use an attachment circuit or device which operates to stabilize the output voltage of the high voltage generating apparatus.

It is often necessary to derive intermediate voltages or voltages lower than the rated output'voltage from such high voltage generating apparatus. Generally, a resistance potentiometer is used for this purpose. However, where the impedance of the intermediate voltage generating circuit is high such measure scarcely affects the output voltage, whereas where the impedance is low, a substantially large current flows through the intermediate voltage generating circuit. Accordingly, variation in the intermediate voltage causes the output voltage to vary, and variation in the load also reflects in the variation of the intermediate voltage.

It is an object of this invention to provide new and improved high voltage generating apparatus which can produce a stable output voltage as well a stable intermediate voltage lower than the output voltage.

Another object of this invention is to provide an improved high voltage generating apparatus of simplified construction.

Yet another object of this invention is to provide a novel high voltage generating apparatus in which high source voltage is prevented from varying the output voltage of the apparatus as the load varies, thus stabilizing the output voltage and by which it is possible to derive out voltages lower than the output voltage withoutaffecting the stability of the output voltage.

A further object of this invention is to provide a novel high voltage generating apparatus which can provide an intermediate voltage without the necessity of using any additional device.

According to this invention there is' provided high voltage generating apparatus comprising a source of high voltage, and a rod shaped nonlinear element of high breakdown voltage, the nonlinear element being connected across the source and being provided with means for deriving an intermediate voltage lower than the output voltage of the high voltage generating apparatus whereby to maintain the output voltage at a substantially constant value.

: BRIEF DESCRIPTION OF THE DRAWINGS FIG. 4 shows load current-load voltage characteristics of a circuit with and without the nonlinear element; A

FIG. 5 shows a connection diagram of a modified high voltage generating apparatus especially suitable for use in a television receiving set FIG. 6 shows a connection diagram of another embodiment of this invention including means for controlling the source voltage in response to the voltage variation in the output of the source FIG. 7 is an exploded perspective view of essential elements of the novel high voltage generating apparatus and FIG. 8 shows a view similar to FIG. 7 but illustrating a modified sliding contact for deriving the intermediate voltage.

DESCRIPTION OF THE PREFERRED EMBODIMENTS With reference first to FIG. 1, the high voltage generating apparatus 10 shown therein comprises a source of high AC voltage 11 and a nonlinear element 12 connected across the source 11. As will be described later in more detail, the nonlinear element 12 is provided with a tap 13 for deriving an intermediate voltage. As shown, a load 15 is connected across nonlinear element 12.

As the nonlinear element 12 is used a rod shaped symmetrical varistor of high breakdown voltage prepared by sintering silicon carbide powder, for example. As shown FIG. 2, the nonlinear element 12 comprises a rod shaped body 21 of uniform cross-section, terminals 22 and 23 secured to the opposite ends of the body, lead wires 24 and 25 connected to terminals 22 and 23 and a ring shaped terminal 26 secured at an intermediate position of the body-for deriving out an intermediate voltage. The position of the intermediate terminal 26 is adjustable along the length of the body 21 as shown by a double headed arrow 29 by loosening a screw 28.

As shown in FIG. 3, the voltage-current characteristic of this nonlinear element is symmetrical with respect to the origin of a rectangular coordinate. Below a threshold value V,, the current increases gradually with the increase in'voltage but beyond the threshold value the current increases abruptly. In other words, as the voltage impressed upon the nonlinear element increases beyond the threshold value the element becomes conductive thus greatly decreasing its resistance.

In the circuit shown in FIG. 1 so long as the crest value of the voltage of source 11 is lower than the threshold value V, of the nonlinear element 12, all output of the source is supplied to load 15 but as the crest value increases beyond the threshold value V, the output from the source will be shunted by the nonlinear element, thus limiting to V, the maximum value of the voltage supplied to load 15.

Turning now to FIG. 4, in the absence of the nonlinear element 12, the load current (I) load voltage (V) characteristic will be shown by a curve a whereas with the nonlinear element the characteristic will be shown by curve b. For a small load current I in a range of from zero to 1,, even when the source voltage is higher than the threshold voltage V, of the nonlinear element, the load voltage V will be limited to the threshold voltage V,. Thus, within a prescribed range of the load, it is possible to obtain a constant output voltage across the opposite terminals of the nonlinear element, thus applying the stabilized constant voltage along the length thereof. For this reason it is also possible to derive a stable constant intermediate voltage from the tap or lead 13 which can be varied according to the position of the ring shaped electrode 26 along the length of the nonlinear element 12.

FIG. illustrates a modified embodiment of this invention suitable for use in a television receiving set. In this embodiment, the output from the source of high voltage AC l1 is supplied to a rectifier circuit 31 and the rectified output thereof is supplied to the anode electrode 33 of a cathode ray tube 32 of the television receiver. Rectifier circuit 31 comprises four diodes 34 to 37 and two capacitors 38 and 39 connected as shown and is constructed to multiply the voltage by a factor of 4. The nonlinear element 12 is connected between the juncture between diodes 34 and 35 of the rectifier circuit 31 and the ground. The intermediate voltage taken out of the nonlinear element 12 is supplied to the focusing electrode 40 of the cathode ray tube.

Although the nonlinear element 12 may be posi tioned on either the load side or the input side of the rectifier circuit 31, where the element is disposed on the load side, as a high voltage is impressed across the element it is necessary to increase the length thereof and hence the physical size of the high voltage generating apparatus. On the other hand, where the nonlinear element is connected to the load side as the voltage impressed across the element is low it is possible to decrease the length thereof. In any case, the use of the nonlinear element provides a stable constant load voltage over a prescribed range of the load current.

FIG. 6 shows another embodiment of the novel high voltage generating apparatus comprising means for controllingthe source 11 in accordance with the variation in the output voltage thereof. A piezoelectric transducer is herein used as the source 11. Elements corresponding to those shown in FIGS. 1 and 3 are designated by the same reference numerals.

The source of high voltage 11 comprises a piezoelectric transducer 42, a parallel resonance circuit 43 including an inductance and a capacitance, a transistor 44 on the input side of the source 11, a transistor 45 with its emitter electrode connected to resonance circuit 43,'a source of DC connectedto the collector electrode of transistor 45, a diode 47 connected between the resonance circuit 43 and the collector electrode of transistor 44, and a DC amplifier 48 connected to a suitable point of the rectifier circuit 31 via nonlinear element 12. The-output of DC amplifier 48 is connected to the base electrode of transistor 45. Thus, the output voltage of source 11 controls the current flowing through the resonance circuit 43 through the action of the nonlinear element 12 to control the driving input to the piezoelectric transducer thereby varying the output voltage of the piezoelectric transducer to compensate for any variation in the source voltage.

FIG. 7 shows an exploded view of essential elements of the novel high voltage generating apparatus. The interior of a casing 50 of a synthetic resin, polypropyrene resin, for example, is divided into three compartments by insulating partition walls 51 and 52. The shorter side walls of the casing are formed with notched 59, 60 and 61 whereas partition walls 51 and 52 are formed with notches 53 to 58. One of the longer side wall is provided with a notch 62. A strip shaped terminal 64 has bent ends and a lead wire 67 is connected to one of the ends. A conductor 69 is helically wound about a rotary body 68 having an operating knob connected thereto by means of a shaft 71.

When assembling the element, terminal strip 64 is disposed in notches 55 and 58, shaft 71 of the rotary body in notches 54 and 57 and nonlinear element 12 in notches 53 and 60 in such a manner that helical condoctor 69 engages the periphery of the nonlinear element and the terminal strip at the same time, and that the rotary body can be moved in the longitudinal direction while maintaining electrical contacts between it and the nonlinear element and the terminal strip.

When the knob 70 on the outside of casing 50 is rotated the contact points between rotary body 68 and nonlinear element 12 are varied gradually to vary the intermediate voltage appearing at lead wire 67. When desired a suitable lid may be provided for the casing 50.

FIG. 8 shows a perspective exploded view of another example of the novel high voltage generating apparatus. Elements identical to or functioning similarly to those shown in FIG. 3 are designated by the same reference numerals. This embodiment is different from that shown in FIG. 7 in that a sliding mechanism is used to derive out the intermediate voltage. More particularly a longitudinal rib 74 is provided on the inner bottom wall of the casing 50 to receive a guide groove 73 on the lower surface of a movable block 72 disposed to move between nonlinear element 12 and terminal strip 64. A generally U shaped sliding contact 71 is secured to the movable block 72 to engage its legs against nonlinear element 12 and terminal strip 64. The block 72 and hence the sliding contact 71 are moved longitudinally of the casing by means of a knob 78 secured to the upper end of a rod 75 extending through a longitudinal slot 77 of a lid 76, the slot 77 being formed above rib 74. Thus, by moving knob 78 along slot 77, the intermediate voltage appearing at lead wire 67 can be varied to any desired value. With this construction, since the movable block 72 is guided by the rib 74, the relative position between the movable block, the nonlinear element and the terminal strip 64 can be always assured without any lateral movement.

It is to be understood that the invention is not limited to the particular embodiments illustrated and that many changes and modifications will be obvious to one skilled in the art. Thus, for example, where direct current is to be supplied to the load the nonlinear element may have an anasymmetical characteristic.

What is claimed is:

1. High voltage generating apparatus comprising a source of high AC voltage, a voltage step-up rectifier circuit connected across said source and comprising a plurality of serially-connected diodes, and a rod shaped nonlinear element of high breakdown voltage, said nonlinear element being connected to said rectifier circuit at a junction between two adjacent ones of said diodes, and having means for deriving an intermediate voltage lower than the output voltage of said rectifier circuit, said deriving means being adapted to be adjustable positioned and fixed along said rod-shaped element to variably set said intermediate voltage.

2. The high voltage generating apparatus according to claim 1 wherein the output voltage of said rectifier circuit is suppliedto the anode electrode of a cathode ray tube of a television receiving set and said intermediate voltage derived out from said nonlinear element is supplied to the focusing electrode of said cathode ray tube.

3. High voltage generating apparatus comprising a voltage controllable source of high voltage, and a rod shaped nonlinear element connected to said source to detect the variation in the output voltage of said source and, in response, to provide an output voltage for controlling said source, said nonlinear element being provided with means for deriving out an intermediate voltage which is lower than the voltage impressed across said nonlinear element, and means, responsive to the output voltage of said nonlinear element, for controlling said source to maintain said output voltage at a substantially constant value.

4. The high voltage generating apparatus according to claim 3 wherein said source includes a piezoelectric transducer, a parallel'resonance circuit for driving said piezoelectric transducer, and a transistor energized by said nonlinear element for controlling the current flowing through said parallel resonance circuit.

5. High voltage generating apparatus comprising a source of high voltage, and a rod shaped nonlinear element having high breakdown voltage, said nonlinear element being connected across said source and being provided with means for deriving out an intermediate voltage lower than the output voltage of said source, said deriving means comprising a terminal strip disposed in parallel with said nonlinear element, a rotatable cylindrical body, a conductor helically wrapped about the periphery of said cylindrical body, said conductor electrically bridging said nonlinear element and said terminal strip, and means for rotating said cylindrical body to move said helically wrapped conductor in the longitudinal direction along said nonlinear element so as to vary said intermediate voltage. 

1. High voltage generating apparatus comprising a source of high AC voltage, a voltage step-up rectifier circuit connected across said source and comprising a plurality of serially-connected diodes, and a rod shaped nonlinear element of high breakdown voltage, said nonlinear element being connected to said rectifier circuit at a junction between two adjacent ones of said diodes, and having means for deriving an intermediate voltage lower than the output voltage of said rectifier circuit, said deriving means being adapted to be adjustable positioned and fixed along said rod-shaped element to variably set said intermediate voltage.
 1. High voltage generating apparatus comprising a source of high AC voltage, a voltage step-up rectifier circuit connected across said source and comprising a plurality of serially-connected diodes, and a rod shaped nonlinear element of high breakdown voltage, said nonlinear element being connected to said rectifier circuit at a junction between two adjacent ones of said diodes, and having means for deriving an intermediate voltage lower than the output voltage of said rectifier circuit, said deriving means being adapted to be adjustable positioned and fixed along said rod-shaped element to variably set said intermediate voltage.
 2. The high voltage generating apparatus according to claim 1 wherein the output voltage of said rectifier circuit is supplied to the anode electrode of a cathode ray tube of a television receiving set and said intermediate voltage derived out from said nonlinear element is supplied to the focusing electrode of said cathode ray tube.
 3. High voltage generating apparatus comprising a voltage controllable source of high voltage, and a rod shaped nonlinear element connected to said source to detect the variation in the output voltage of said source and, in response, to provide an output voltage for controlling said source, said nonlinear element being provided with means for deriving out an intermediate voltage which is lower than the voltage impressed across said nonlinear element, and means, responsive to the output voltage of said nonlinear element, for controlling said source to maintain said output voltage at a substantially constant value.
 4. The high voltage generating apparatus according to claim 3 wherein said source includes a piezoelectric transducer, a parallel resonance circuit for driving said piezoelectric transducer, and a transistor energized by said nonlinear element for controlling the current flowing through said parallel resonance circuit. 